import java.util.Scanner;
public class yi{
	public static void main(String args[])
	{
		Scanner cin =new Scanner(System.in);
		int grade = cin.nextInt();
		if(grade>=90)
			System.out.println("A");
		else if(grade<90&&grade>=80)
			System.out.println("B");
		else if(grade<80&&grade>=70)
			System.out.println("C");
		else if(grade<70&&grade>=60)
			System.out.println("D");
		else
			System.out.println("E");
	}
}